CVE-2026-9699

EUVD-2026-39778
Mattermost Plugins versions <=11.6 10.18.11 11.3.6 11.6.5.0 fail to sanitize error responses from the OpenAI API before logging, which allows a user with access to server logs or support packets to obtain a valid or partially reconstructable OpenAI API key via inspection of mattermost.log entries generated during authentication failures. Mattermost Advisory ID: MMSA-2026-00609
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
MattermostCNA
6.8 MEDIUM
NETWORK
LOW
HIGH
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mattermostmattermost
𝑥
≤ 10.18.11
CNA
mattermostmattermost
𝑥
≤ 11.3.6
CNA
mattermostmattermost
𝑥
≤ 11.6.5
CNA
Common Weakness Enumeration
References
https://mattermost.com/security-updates